论文标题
Hatsugai-Kohmoto-BCS模型中的两阶段超导性
Two-stage superconductivity in the Hatsugai-Kohmoto-BCS model
论文作者
论文摘要
强相关电子中的超导性可以从超出Landau的费米液体范式之外的正常状态中出现，通常被称为“非Fermi液体”。虽然非弗米液体的理论尚未结论性，但最近对可溶解的hatsugai-kohmoto（HK）模型的一项研究表明，非弗尔米液体基态的绿色功能类似于Yang-rice-rice-Zhang ansatz for cuprates [P. P. [P. P. [P. W. Phillips，L。Yeo和E. W. Huang，Nat。物理。 $ \ bf {16} $，1175（2020）]。与哈伯德模型中现场库仑排斥的影响相似，HK模型中的排斥相互作用将动量空间划分为三个部分：空，单占单占和双人的区域，这些区域彼此之间相互分离，而不是两个不同的Fermi表面。在存在额外的Bardeen-Cooper-Schrieffer（BCS） - 型配对相互作用的相互作用的相互作用时，我们表明该系统表现出“两级超导性”特征，随着温度的降低：一阶超导过渡发生在$ t _ {\ rm c} $下的一阶超导向过渡时，突然的订单会增加一个序列，该订单的范围较高，该订单会增加一定的参与者，该订单的参与量会增加一定的参与。 $ t _ {\ rm c}^{\ prime} <t _ {\ rm c} $。在第一阶段，$ t _ {\ rm c}^{\ prime} <t <t <t _ {\ rm c} $，成对功能出现，熵仅在两个费米表面附近释放；在第二阶段，$ t <t _ {\ rm c}^{\ prime} $，配对函数变得很重要，并且该熵在费米海的深处（单占）区域进一步释放。在金茨堡 - 兰道理论中分析了相变。我们的工作为强相关的电子中非常规超导性提供了新的启示。
Superconductivity in strongly correlated electrons can emerge out from a normal state that is beyond the Landau's Fermi liquid paradigm, often dubbed as "non-Fermi liquid". While the theory for non-Fermi liquid is still not yet conclusive, a recent study on the exactly-solvable Hatsugai-Kohmoto (HK) model has suggested a non-Fermi liquid ground state whose Green's function resembles the Yang-Rice-Zhang ansatz for cuprates [P. W. Phillips, L. Yeo and E. W. Huang, Nat. Phys. $\bf{16}$, 1175 (2020)]. Similar to the effect of on-site Coulomb repulsion in the Hubbard model, the repulsive interaction in the HK model divides the momentum space into three parts: empty, single-occupied and double-occupied regions, that are separated from each other by two distinct Fermi surfaces. In the presence of an additional Bardeen-Cooper-Schrieffer (BCS)-type pairing interaction of a moderate strength, we show that the system exhibits a "two-stage superconductivity" feature as temperature decreases: a first-order superconducting transition occurs at a temperature $T_{\rm c}$ that is followed by a sudden increase of the superconducting order parameter at a lower temperature $T_{\rm c}^{\prime}<T_{\rm c}$. At the first stage, $T_{\rm c}^{\prime}<T<T_{\rm c}$, the pairing function arises and the entropy is released only in the vicinity of the two Fermi surfaces; while at the second stage, $T<T_{\rm c}^{\prime}$, the pairing function becomes significant and the entropy is further released in deep (single-occupied) region in the Fermi sea. The phase transitions are analyzed within the Ginzburg-Landau theory. Our work sheds new light on unconventional superconductivity in strongly correlated electrons.
